System for changing the output response characteristics of an acoustic input

ABSTRACT

A SECOND SYSTEM IS DISCLOSED INCORPORATING A FREQUENCY DIVIDER FOR DIVIDING A SOUND SIGNAL INTO PREDETERMINED FREQUENCY RANGES. EACH FREQUENCY RANGE IS SELECTIVELY SUBJECTED TO PHASE SHIFTING AND/OR AMPLITUDE MODULATION TO PRODUCE A DESIRED EFFECT. THE MODULATED FREQUENCY RANGES ARE RECOMBINED IN A MIXER AND THE MIXED SIGNAL IS APPLIED TO APPROPRIATE AMPLIFYING THE TRANSDUCING MEANS THROUGH A PARALLEL ARRANGEMENT OF A RESISTANCE AND A REVERB SYSTEM. ADJUSTMENTS ARE PROVIDED FOR ALTERING THE INTER RANGE PHASE RELATIONSHIP AND FOR INDUCING TREMOLO IN SELECTED FREQUENCY RANGES, TREMOLO IS ALSO SELELCTIVELY PROVIDED FOR THE COMBINED AND MIXED FREQUENCY RANGES.   D R A W I N G

EJMUJBZ P. R. BARNUM SYSTEM FUR CHANGING THE OUTPUT RESPONSE March' 6. 1973 CHARACTERISTICS OF' AN ACOUSTIC INPUT 4 Sheets-Sheet l Filed Oct. l2, i971 Il l l l l l l l |1|| mcwl mrml dmc u 1 m 3 V -vN Nmw NN I l l l l l I I II'JIIIIIL f JS.

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102 3 73 mo f a5 Hoo Ann noo Mixen OKLPPUT REVERS OSC o 05C f117 03 moa j j 114? y ab non Anp Moo oec 4 osa 5w J L 5w United States Patent O SYSTEM FOR CHANGING THE OUTPUT RE- SPONSE CHARACTERISTICS F AN ACOUS- TIC INPUT Phillip R. Barnum, Mesa, Ariz., assignor to .laines E. Breene, Chandler, Ariz. Filed Oct. 12, 1971, Ser. No. 188,418 Int. Cl. H0311 7/ 00; Glflh I 00 U.S. Cl. 179--1 .I 14 Claims ABSTRACT 0F Tlf-IE DISCLOSURE BACKGROUND `OF THE INVENTION The present invention pertains to sound generating systems, and more particularly, to a system for creating desired sound effects when energized by a conventional musical instrument.

The utilization of amplifiers in combination with musical instrumentation is a well developed art; further, special sound effects have been generated through the utilization of oscillators and the like generating tones or sounds to be utilized in combination with an instrument. Embodied in this general prior art are numerous attempts to impart tones and sound effects to a musical instrument to render the sound similar to another instrument. These attempts have, for the most part, been generally unsuccessful in that the sophistication of electronic circuitry required to detect the frequency of the note being played and converting that frequency into the proper tone and harmonic frequencies of the instrument to be imitated has resulted in an extremely complex, cumbersome, and expensive system which is not altogether successful in its simulation of another instrument.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a sound system that may be utilized to simulate the sound of a desired instrument.

It is another object of the present invention to provide a sound system that is capable of receiving a signal imparted by an instrument and transforming the signal into modified form to render a pleasing effect.

It is still another object of the present invention to provide a sound system incorporating means to separate the frequencies of a detected sound and operate upon the separated frequencies to effect an overall sound change.

It is still another object of the present invention to provide a sound system wherein frequencies of a detected sound are divided and operated upon independently to subsequently be recombined to form a new sound that may simulate an instrument unlike the instrument generating the original sound.

It is still another object of the present invention to provide a sound system wherein a detected sound may be modified to incorporate certain and desirable sound effects,

such as tremolo and reverberatory effects.

These and other objects of the present invention will ICC become apparent to those skilled in the art as the description thereof proceeds.

SUMMARY OF THE CHOSEN EMBODIMENT The present invention is a sound system incorporating a frequency dividing section wherein an incoming sound signal is divided into three frequency ranges, each range subsequently being operated upon independently of each other range. In a specific embodiment chosen for illustration, the high and low ranges are each subjected to modulation, the frequency of modulation depending upon a desired tremolo effect; the low frequency may further be phase-shifted by an oscillator if it is desired to impose still another effect on the ultimate sound. The three frequencies thus operated upon independently are then mixed and the mixed signal again subjected to modulation of a varying degree, depending on the desired tremolo offect. The mixed signal is then applied to a preamplifier, while a parallel circuit is provided to enable the generation of a reverberatory effect through a delay in recombination of the delayed signal with the original signal. The resulting signal is amplified and applied to an appropriate transducer. The frequency of the tremolo effect is variable and may be preselected to render a desired sound while the phase of the respective frequency ranges may be altered with respect to each other. In the specific embodiment described in detail, the high range frequencies and the mixed frequencies are maintained in phase while the 10W frequencies are deliberately phase-shifted This phase shift may be rendered variable by the implementation of a variable phase shifter interposed in series with the low frequency signal.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention may more readily be described by reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of a sound system constructed in accordance with the teachings of the present invention.

FIG. 2 is a circuit diagram of a typical preamplifier for use in the block diagram of FIG. l.

FIG. 3 is a circuit diagram of a tremolo oscillator incorporating a predetermined phase relationship between specific frequency bands and representing certain blocks of FIG. 1.

FIG. 4 is a schematic circuit diagram of a typical mixer for utilization in the block diagram of FIG. 1.

FIG. 5 is a circuit diagram of a unique driver circuit used in the system of the present invention and incorporated in the block diagram of FIG. 1.

FIG. 6 is a schematic block diagram of a modification of the block diagram of FIG. 1 incorporating the teachings of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings, and particularly to FIG. 1, a preamplifier 1f) is provided to receive a signal applied to the terminal 11 from a suitable source. The signal applied to terminal 11 may be derived from any instrument whose sound has been appropriately transduced, such as by a microphone, or through the utilization of other types of transducers, such as contact type, etc. The sound derived from the instrument is transduced to an appropriate electrical signal. The electrical signal thus applied to the terminal 11 is divided into three frequency ranges: low, mid, and high. Each of the respective frequency ranges is amplified in a preamplifier 12, 13, and 14, respectively. IThus, the amplified frequency ranges are each available for manipulation in accordance with a desired sound effect. A tremolo section 17 includes tremolo modulator 18 for the low frequency range, tremolo modulator 19 for the high frequency range, and

tremolo modulator 20 for the mixed signal to be described. Each of these modulators 18, 19, and 20 derive the tremolo frequency or tremolo speed as it is referred to in the art from an oscillator 22. The signal from the oscillator 22 is appropriately shaped by wave shaper 23 and is applied to a phase splitter 24, which will be described more completely hereinafter. The phase split tremolo signal is thus applied to tremolo modulator 18, 19, or 20.

The low frequency range may also be utilized as a means to simulate the particular type of sound generated from a speaker known as a Leslie speaker. While this phenomena will be described more completely hereinafter, a variable phase shifter 2S may be incorporated in the low frequency range section, the phase shifting of which may be determined by the frequency of an oscillator 28. The phase shift imposed by the variable phase shifter 25 would result in a frequency shift of the low frequency range of from 20 to 200 hertz. Further, the rate of frequency change would be approximately 6 to 9 times per second. Although it Will be obvious that the frequency ranges herein described may vary with regard to the spectrum of frequencies considered within each range, I have found that the usual frequencies considered to be low, mid, or high range are appropriate in Working with the sound system of the present invention. Thus, as herein described, high frequencies are considered from 2000 to 10,000 hertz, midrange frequencies are considered from 600 to 2000 hertz, while the loW frequencies are generally considered from approximately 40 to 600 hertz.

It may be noted that the low and high range frequencies have been modified while the mid-range frequencies have until now remained unchanged. The separated and modilied signals are thus passed to a mixer 30 through potentiometers 31, 32 and 33 that may be utilized to balance or otherwise alter the relative signal strength among the low, mid, and high freqeuncy ranges. The mixed signal derived from the mixer 30 is applied to the third tremolo modulator 20. The relationship of the modulation in modulator 20 as compared to the modulation in modulators 18 and 19 will be described more fully hereinafter. The combined signal emanating from the mixer 30 is thus again subjected to the modification of a desired tremolo effect which, of course, may be preselected to be completely inoperative, thus passing the straight signal unmodulated to a volume potentiometer 36. The signal at 36 is applied to amplifier 38 through a resistor 39 and a reverb effect system paralleling the resistor 39. This reverb effect system incorporates a reverb driver 40, a reverb effect unit 41, and a reverb amplifier 42. As mentioned previously, the effects of the reverb system provide a delaying effect to the signal applied to the amplifier 38. Thus, the signal and its delayed counterpart are successively applied to the amplifier, resulting in an echo effect. The output of the amplifier 38 is applied to a conventional power amplifier 45 and subsequently to a suitable transducer 46. 4

Referring now to FIG. 2, a typical preamplifier for utilization in the block diagram of FIG. l is shown. The input terminal 11 is shown for receiving an input signal as previously described. The signals applied to the base of transistor Q1. The transistor Q1 is connected in an emitter-follower configuration with the output thereof applied to a typical freqeuncy dividing network of resistors and capacitors, each network for passing a predetermined frequency range to a corresponding one of the preamplifiers 12, 13, and 14. The preamplifiers may be of conventional design and may be either discrete circuits or formed of readily available integrated circuits. The outputs of the low, mid, and high freqeuncy preamplifiers 12, 13, and 14 appear respectively at terminals 50, 51, and 52.

Referring now to FIG. 3, the tremolo terminals 50 and 52 operate at two of the three inputs to the circuit of FIG. 3. The terminal S receives the mixed signal after the three frequency ranges have been recombined in the mixer 30 (FIG. l). An oscillator, including transistor Q2, provides the tremolo frequency or speed and is variable by adjusting the potentiometer 56. The magnitude of the modulation to be derived through the utilization of the oscillator may be adjusted through the utilization of the potentiometer 57 from an amplitude of substantially of the total sound amplitude to zero modulation where no tremolo effect is evident. The waveforms derived from the oscillator are amplified through transistor Q3 and applied to the base of Q4; however, it will be noted that both the emitter and the collector electrodes of transistor Q4 are utilized to transmit the amplified waveform from the oscillator to the respective frequency range signals applied at the terminals 50 and 52. The collector electrode of the transistor Q4 is connected through a manual switch S8 to the control electrode of a Field Effect Transistor (F.E.T.) Q5. A potentiometer 60 provides variable attenuation of the signal applied to the transistor Q5 and may be termed a depth control for adjusting the amount of modulating effect imposed on an incoming sound signal.

Similarly, the emitter electrode of the transistor Q4 is connected through a potentiometer 61 (depth control) and a manual switch 62 to the control electrode of F.E.T. Q5. The emitter electrode of Q4 is also connected through still another potentiometer or depth control 63 and manual switch 66 to the control electrode of F.E.T. Q5. It may therefore be noted that the signal derived from the transistor Q4 is applied to the three F.E.T.s Q5, Q5 and QS; however, the signal from Q4 applied to Q5 is 180 out of phase with the signal applied to F.E.T.s Q5 and QS". The low frequency range signal applied to the terminal 50 is connected to the base of transistor Q6 and amplified, while the modulation of the tremolo oscillator is imposed thereon through the connection of the F.E.T. Q5 with the transistor Q6. Similarly, the signals applied to terminals 52 and 55 are applied to the base electrodes of transistors Q6' and Q6", while the signals amplified therein are modulated by the tremolo modulation signals applied to the respective transistors by F.E.T.s Q5 and Q5". Therefore, the low range sound signals applied to the terminal 50 are modulated at the frequency and amplitude determined by the adjustments available at the tremolo oscillator and the resulting modulated signal applied to the low frequency range output terminal 68. In a similar manner, the high range sound signals applied to terminal 52 and the mixed or tone sound signals, applied to the terminal 55 are each modulated and presented to their corresponding output terminals 69 and 70. It may be noted that the modulation provided to the low range signals is out of phase with that modulation applied to the high range signals and the mixed signals. This phase differential is fixed in the embodiment shown in FIG. 3; howe-ver, it will be understood that a variable phase shift may be imposed between and among the three sound signals being applied to the circuit of FIG. 3 to derive desired sound effects. The switches 58, 62, and 66 are each provided to shunt the control electrode of the corresponding F.E.T.s to ground to enable the operator to remove the tremolo effect from any one or all of the frequency range channels, again to produce a desired effect.

Referring now to FIG. 4, a typical mixer circuit appropriate for utilization in the system of the present invention is shown. The mixer is generally conventional and receives the signals from all the frequency ranges at terminal 51. The amplifier 75 may take any of numerous well known forms and may, for example, be formed from readily available integrated circuit chips, such as Motorola Mc 1303. The amplified output signal available at terminal 55 is then applied to the circuit previously described in connection with FIG. 3.

As mentioned in connection with the block diagram of FIG. l, a reverb system including a reverb driver 40, a reverb unit 41, and a reverb amplifier 42, permits the imposition of a delay to the sound resulting in certain desirable sound effects. Reverb units are well known in the art and typically utilize a variety of sonic delay techniques. One such technique incorporates a coiled wire having a transducer at the ends thereof that can be utilized as a sonic delay line to impose a predetermined delay to the signal. Such delay lines are readily available; however, such units generally exhibit the unfortunate characteristic of a variable impedance. The input impedance of such units is a function of frequency and, as shown in FIG. 5, an inductive winding couples the input signal to the reverb unit. The reverb driver of FIG. overcomes the above problems resulting from the variable impedance of such reverb units. The mixed and modulated sound signal is applied to the terminal 80 of the driver and is appropriately amplified by transistors Q7, Q8, and Q9; however, it may be noted that transistors Q8 and Q9 are complementary types. Series connected capacitor 82 and resistor 83 are connected between the base electrode at transistor Q7 and a summing point 85 forming one side of the reverb unit 41. A resistor 87 parallel the reverb unit between a reverb unit input terminal 88 and the summing point 85; resistor 89 is connected in series with the reverb unit 41 input and is connected between summing point 85 and ground. By proper choice of the resistors 83, 87, and 89 as well as a capacitor 82 relative to the power requirements and impedance variation of the reverb unit 41, a constant current is provided by the driver of FIG. 5 regardless of the impedance variation of the reverb unit 41. For example, a typical reverb unit presently available on the market will include an impedance variation of from 2 to 22 ohms. Under those circumstances, the following values are typical for the element indicated:

Capacitor 82=2 microfarads Resistor 83=27K ohms Resistor 87 :20 ohms Resistor 89=1 ohm.

The resistor 89 provides negative feedback voltage at the input of the reverb unit 41. The signal present for feedback is a function of the current through the resistor 89; at low frequency, the input impedance of the reverb unit 41 appears low, thus resulting in a given IR drop across the resistor 89. As the frequency of the applied signal increases, the input impedance of the reverb unit 41 appears greater, thus reducing the IR drop across the resistor 89. The input voltage versus frequency characteristic maintainsa constant drive current to the reverb unit 41; resistor 87 prevents what would otherwise be an open circuit in the event of removal of the reverb unit.

Referring now to FIG. 6, a modification of the system of the present invention is shown incorporating the features of FIG. l in a somewhat expanded form. Input terminal 93 receives the original sound signal which is subsequently frequency divided and applied to frequency range preamplifers 95, 97, and 99. Each of the signals being amplified by one of the amplifiers 95, 97, 99 may be phase modulated in a phase modulator 101, 102, 103. Each of the phase modulators 101-103 may be formed using conventional circuit technology and utilizing a continuously variable oscillator 104, 105, 106, respectively, that may be characteristically a zero to 12 hertz oscillator to drive and control the modulation frequency of the respective phase modulator. A switch 110 may be provided to enable all the phase modulators 101-103 to be driven from the oscillator 106 when it is desired that the modulation of all frequency ranges be in phase. The phase modulated signals of the respective frequency ranges are then applied to amplitude modulators 112, 113, and 114. Each of the modulators 112-114 is driven by a corresponding oscillator 116, 117, and 118 respectively. The switch 120 is provided to enable all the amplitude modulators 112- 114 to be driven from a single oscillator 118. The single oscillator 118 may be utilized to drive the respective amplitude modulators when it is desired to amplitude modulate all three frequency ranges at an identical frequency. It will be obvious to those skilled in the art that a variety of oscillator configurations may be utilized in the embodiment chosen in FIG. 6 and that under certain circumstances the functions of the phase modulation oscillators and amplitude modulation oscillator may be combined.

The signal originally applied to terminal 93 has thus been divided into frequency ranges, each of Which has been independently phase modulated and amplitude modulated. The phase and amplitude modulated signals are then recombined in a mixer and applied to an output amplifier 128 through a resistor 129 and a paralleling reverb unit 130. The reverb unit may be as described previously in connection with the diagram of FIG. l; the resulting amplified signal from the amplifier 128 is then applied to an appropriate transducer 131.

.By separating the sound signal derived from an instrument into frequency bands or ranges and phase and/or amplitude modulating signals in these frequency ranges, a great variety of effects can be imposed on the sound. For example, the sound reaching a listeners ear from a mechanically rotating speaker, such as the previously mentioned Leslie speaker, is the result of complex interaction of numerous factors, including frequency modulation induced by the Doppler effect of the speaker, beat frequencies, phase and amplitude modulation. By inducing a frequency shift of from 20 to 200` hertz at a rate of approximately 6 to 9 hertz through the utilization of oscillator 28 and phase shift modulator 25 of FIG. l, coupled with the tremolo modulation afforded by the system of the present invention, the sound of the previously mentioned rotating speaker system can be duplicated. Further, among the great variety of musical sounds that can be imposed on an otherwise unrelated tone, a con- `ventional contact-type microphone can be utilized with a piano to generate organ sounds. It Will be apparent to those skilled in the art that many modifications c-an be made in the system chosen for specific illustration without departing from the scope of the present invention.

I claim:

1. In a sound system for manipulating or amplifying an electrical signal corresponding to an acoustical signal, the improvement comprising: a frequency divider connected to receive said electrical signal for dividing said electrical signal into a plurality of range signals, each within a predetermined frequency range; an oscillator for producing a tremolo signal having a predetermined frequency and amplitude; an amplitude modulator connected to said oscillator and connected to receive at least one of said range signals for amplitude modulating said range signal with said tremolo signal; a phase shifting circuit connected to receive said range signals for shifting the phase of at least one of said range signals relative to the other range signals; a mixer connected to receive said range signals from said amplitude modulator and said phase shifting circuit for mixing said range signals to produce an output signal.

2. The combination set forth in claim 1, wherein said tremolo signal is amplified in a transistor having a collector and an emitter, and wherein said collector is connected to amplitude modulate one of said range signals, and said emitter is connected to amplitude modulate another of said range signals whereby said range signals are modulated out of phase with respect to each other.

3. The combination set forth in claim 1, including a second oscillator and wherein said phase shifting circuit is a variable phase modulator connected to said second oscillator for varying the phase of at least one of said range signals relative to the other range signals at a frequency determined by said second oscillator.

4. The combination set forth in claim 1, including a reverb amplifier and an output resistor and wherein said output signal is applied in parallel to said reverb amplilier and said output resistor.

S. The combination set forth in claim 2, including a reverb amplifier and an output resistor and wherein said output signal is applied in parallel to said reverb amplier and said output resistor.

6. The combination set forth in claim 3, including a reverb amplifier and an output resistor and wherein said output signal is applied in parallel to said reverb amplier and said output resistor,

7. In a sound system for manipulating or amplifying an electrical signal corresponding to an acoustical signal, the improvement comprising: a frequency divider connected to receive said electrical signal for dividing said electrical signal into high, mid, or low range signals, each within a predetermined frequency range; an oscillator for producing a tremolo signal having a predetermined frequency and amplitude; an amplitude modulator connected to said oscillator and connected to receive said high range signal and said low range signal for amplitude modulating said high and low range signals with said tremolo signal; a phase shifting circuit connected to receive said range signals for shifting said high range and low range signals relative to each other; a mixer connected to receive said range signals from said amplitude and modulator and said phase shifting circuit for mixing said range signals to produce a mixer signal; means connecting said mixer signal to said amplitude modulator for amplitude modulating said mixer signal.

8. The combination set forth in claim 7, wherein said tremolo signal is amplied in a transistor having a collector and emitter and wherein said collector is connected to amplitude modulate said low range signal, and said emitter is connected to amplitude modulate said high range signal whereby said high and low range signals are modulated 180 out of phase with respect to each other.

9. The combination set forth in claim 7, including a second oscillator and wherein said phase shifting circuit is a variable phase modulator connected to said second oscillator for varying the phase of at least one of said range signals relative to the other range signals at a frequency determined by said second oscillator.

10. The combination set forth in claim 7, including a reverb amplifier and an output resistor and wherein said output signal is applied in parallel to said reverb ampli- Iier and said output resistor.

11. In a sound system for manipulating or amplifying an electrical signal corresponding to an acoustical signal, the improvement comprising: a frequency divider connected to receive said electrical signal for dividing said electrical signal into a plurality of range signals, each within a predetermined frequency range; a plurality of oscillators, each corresponding to a different one of said range signals, and each oscillator for producing a tremolo signal; a plurality of amplitude modulators, each corresponding to a different one of said range signals, each connected to a different one of said oscillators and each connected to receive a different one of said range signals for amplitude modulating said range signals with said tremolo signals; a second plurality of oscillators, each corresponding to a different one of said range signals; a plurality of phase modulators, each corresponding to a different one of said range signals, each connected to a different one of said second plurality of oscillators and each connected to receive a different one of said range signals for changing the phase of said range signals relative to each other at a frequency determined by said second plurality of oscillators; a mixer connected to receive said range signals from said amplitude modulators and said phase modulators for mixing said range signals to produce an output signal, a reverb amplifier and an output resistor connected in parallel to receive said output signal.

12. The combination set forth in claim 11, wherein said first plurality of oscillators oscillate at the same frequency and in phase with each other.

13. The combination set forth in claim 11, wherein said second plurality of oscillators oscillate at the same frequency and in phase with each other.

14. The combination set forth in claim 11, wherein said first plurality of oscillators oscillate at the same frequency and in phase with each other and wherein said second plurality of oscillators oscillate at the same frequency and in phase with each other.

References Cited UNITED STATES PATENTS 3,272,906 9/1966 De Vries 84-l.24 3,553,338 1/1971 Holman Sit- 1.24 3,629,484 12/1971 Suzuki 84l.24 3,524,376 8/1970 HeytOW 84-124 KATHLEEN H. CLAFFY, Primary Examiner I. B. LEAHEEY, Assistant Examiner U.S. Cl. X.R. 84-124; 179-1 M 

